Apparatus for the grinding of workpieces, especially tools

ABSTRACT

Appliance for the machining of workpieces, especially tools, such as, for example, for the grinding of drills, with a machining device, for example a double grinding unit, and with a receiver assigned to this and intended for the workpiece. The machining device is assigned a basic stand for the guidance of a carriage, to which is fixed a further guide serving for guiding a further carriage which is itself assigned a lathe attachment or rocker holder with an axis of rotation (B), which is connected to a bearing pedestal or a rocker, on which the receiver or a quick-change holder is arranged.

The invention relates to an appliance for the grinding of workpieces,especially tools, such as, for example, for the grinding of drills, witha machining device, for example a double grinding unit, and with areceiver assigned to this and intended for the workpiece

The main problem of appliances of this type is to bring the workpiece tobe machined to an exact and desired angle relative to the machiningdevice and to maintain it there. Even today, for example, drills areresharpened by hand on a grinding block, how the drill is moved inrelation to the grinding wheel still being left to the skill andexperience of the machinist. The cutting geometry plays a veryconsiderable part in these very situations.

The inventor's object was to develop an above-mentioned appliance, bymeans of which a workpiece to be machined can be brought at any angle upto a corresponding machining device, so that extremely versatilemachining becomes possible.

To achieve this object, the machining device is assigned a basic standfor the guidance of a carriage, on which is fixed a further guideserving for guiding a further carriage which is itself assigned a latheattachment or a rocker holder with an axis of rotation, connected to abearing pedestal, on which the receiver or a quick-change holder isarranged.

The carriages moveable in the guides as a rule execute a movement in thex-axis and y-axis respectively. The two axes of rotation allow theworkpiece to be machined to be assigned to all the other angles of thisplane.

In a preferred exemplary embodiment, the bearing pedestal is soconnected to the lathe attachment that an axis of rotation is formedhere too.

A pivoting of the bearing pedestal through 180° in the C-axis therebybecomes possible. This guarantees any possible angular position of theworkpiece in relation to the machining device.

In addition, the receiver and bearing pedestal will also form yetanother axis of rotation with one another. Since the axis of thereceiver is exactly in line with the axis of the lathe attachment, thislast-mentioned axis of rotation makes it possible to insert into thereceiver longer workpieces to be machined which would otherwise strikeagainst the lathe attachment when being inserted through the receiver.

In a preferred exemplary embodiment, the receiver itself is rotatableabout its longitudinal axis and, furthermore, forms an axis of rotationwith a fork. The fork connects the receiver to the bearing pedestal.

All the axes of rotation are to be assigned corresponding scale rings,and moreover it is intended to make it possible to release theindividual rotatable parts by means of quick-acting chucking levers orclamping screws.

The guides for the carriages are so designed that they consist of athreaded spindle and of two guide rails. The threaded spindle and guiderails pass through the carriages, the threaded spindle meshing with acorresponding internal thread in the carriage. The guide rails run freeof play and are sealed off against dirt by means of concertinas.

Each threaded spindle is assigned a rotary grip with appropriatescaling, this rotary grip rotating the threaded spindle. A fineadjustment of the carriage thereby becomes possible. At the same time,the scaling can be reset to zero.

However, it is also intended to provide a rapid adjustment of eachcarriage. For this, a lever with an appropriate engagement profile forthe threaded spindle passes through the carriage. When this lever islifted out counter to the force of a spring or a cup-spring assemblyand, if appropriate, locked by pivoting, the engagement with thethreaded spindle is cancelled and the carriage can be moved along on theguide rails. Fixing near the desired position is then obtained again byreleasing the lever, so that the profile engages into the thread flightsof the threaded spindle. Fine adjustment then takes place once more viathe rotary grips.

Moreover, all the rotatable and moveable parts are clampable, whether bycorresponding clamping screws or by quick-acting chucking levers.

In a further embodiment, the quick-change holder possesses aquick-acting clamping bolt which is received in a correspondingreceiving bore of the rocker holder. When it is desired to exchange anentire quick-change holder, the quick-change holder to be removed can bedrawn out of the receiving bore of the rocker holder, for example by therelease of a corresponding clamping screw.

According to the invention, an indexing drum is inserted in aquick-change holder. Additionally, reverse grinding is possible by meansof a 12-division. It is possible, for example, to insert a quick-changeholder with a jaw chuck into the rocker holder.

This ensures an accurate plane and concentric running of the workpiece,since all the parts are connected firmly to one another. For thealignment of drill bits for example, a magnifying glass or an aligningholder can also additionally be assigned.

In this second embodiment of the invention, the entire working device isconnected exchangeably to the corresponding carriage via a rockerholder. For this, there projects from the carriage a corresponding guidebolt which engages into the rocker holder and which is fixed there, forexample by means of a clamping screw. The rocker holder, together withthe quick-change holder and a rocker described below, is rotatable aboutthis guide bolt.

Arranged between the rocker holder and the quick-change holder is arocker which passes through the rocker holder and which forms with thisa further axis of rotation extending approximately perpendicularly tothe axis of rotation about the guide bolt. As described above, thequick-change holder too is to be connected releasably to the rocker. Itis thereby possible to exchange receiver units for different workpiecesvery quickly and without much trouble.

The quick-change holder itself forms an axis of rotation with therocker, this axis of rotation preferably extending approximatelyparallel to, but radially offset in relation to, the axis of rotation ofthe rocker. Moreover, this quick-change holder is so designed that itrotates about the axis of rotation just mentioned in a plane parallel tothe main axis of rotation of the rocker holder, an arm then projectingapproximately perpendicularly to this plane and holding the receiver forthe workpiece there.

The longitudinal axis of this receiver is then itself arranged in aplane approximately parallel to the main axis of rotation of the rockerholder.

Preferably, the quick-change holder is likewise located by means of areceiving bolt in a receiving bore of the rocker and is held there witha clamping effect. This receiving bolt is then preferably assigned twoscales, one scale serving for setting the quick-change holder and theother scale for the clearance-angle setting for surface grinding.

The double grinding unit possesses a locating spring and a clampingbore. This can be inserted and clamped in a locating groove on themachine table. A pivoting of the double grinding unit into variouspositions is thereby possible.

The present appliance is suitable above all for the grinding ofsingle-bit, two-bit and multi-bit drilling tools made of HSS and HM andother materials. It is does not matter whether these drilling tools areof the left-hand or right-hand cutting type. Depending on the chuckingsystem, diameters of 0.5 mm to 42 mm can be machined, and the pointangle can be 0° to 180°. Sharpening the drilling tool to a point isreadily possible. The clearance angle is from 0° to 20° for cylindricalgrinding and from 0° to 60° for surface cutting.

Further possible uses are single-bit milling with a point angle of 0° to180° and the grinding of outer radii from the center and reliefgrinding.

Furthermore, centering tools and countersinking tools of all types canbe machined. The machining of milling cutters with a diameter of 2 mm to140 mm is possible both on their end face and on their circumference.Moreover, lathe, plane and forming-lathe cutters made of HSS or HM, butalso progressive cutting tools can be ground.

This list is merely illustrative.

Further advantages, features and details of the invention emerge fromthe following description of preferred exemplary embodiments and withreference to the drawing; in this:

FIG. 1 shows a partially sectional side view of a grinding deviceaccording to the invention;

FIG. 2 shows a top view of the grinding device according to FIG. 1;

FIG. 3 shows a partial front view of the grinding device;

FIG. 4 shows a partially sectional side view of a further exemplaryembodiment of a grinding device;

FIG. 5 shows a top view of parts of the grinding device according toFIG. 4;

FIG. 6 shows a partial front view of the grinding device according toFIG. 4;

FIG. 7 shows a partially sectional side view of a working deviceaccording to the invention;

FIGS. 8-10 show embodiments of quick-change holders.

According to FIG. 1, a grinding device R possesses a double grindingunit 1 consisting essentially of a motor block 2, via which a grindingwheel 3 and 4 is driven on each of the two sides. The double grindingunit 1 includes, furthermore, a bearing frame 5 which rests on a basicstand 6 (see FIG. 3).

The bearing frame 5 is retained via corresponding screws by means ofquick-acting clamping levers 7 which pass through long holes 8represented by broken lines.

The double grinding unit is thus designed displaceably, and furthermoreit can be pivoted in reverse into three positions, each rotated through90°. This affords a time saving during the changeover of the grindingwheels.

A drill receiver as part of a working device P is designated as a wholeby 9 in FIG. 1. This drill receiver 9 is fixed in a bearing pedestal 10which is connected to a lathe attachment 12 via a screw bolt 11. Thislathe attachment 12 is arranged on a carriage 13 which is moveable alonga guide 14. At the same time, according to FIG. 2, this guide 14consists essentially of a middle threaded spindle 15 and of two lateralguide rails 16 and 17. Both the guide rails 16 and 17 and the threadedspindle 15 pass through the carriage 13, but the threaded spindle 15meshes with a corresponding internal thread in the carriage 13. Theguide rails 16 and 17 run free of play and are protected against dirt.

The coarse setting of the carriage 13 is obtained as result of amovement along the guide 14, a lever 20 being pivoted counter to theforce of a spring 21 out of its engaged position with the threadedspindle 15. As soon as the desired position is reached approximately,the lever 20 is pivoted back so that its appropriately profiled end faceengages into the thread flights of the threaded spindle 15. The finesetting of the carriage position can now take place, this being carriedout by means of a corresponding rotary grip 22 with a scaling 23. Thethreaded spindle 15 is rotated by means of this rotary grip 22, whereasthe carriage 13 is held by the guide rails 16 and 17. The adjustment ismade within the 0.01 mm range.

The Y-axis guide 14 rests on a carriage 25 which is connected to thebasic stand 6 via guides 27 and 28 and through which a threaded spindle29 passes.

The carriage 25 is guided on the basic stand 6 in a similar way to thatdescribed with regard to the carriage 13. Here too, the rapid adjustmentis made by a lever 31, whilst the fine setting is carried out by arotary grip 32 with a corresponding scaling 33. The covers of the guides27, 28 are received a concertina 19.

The following possibilities of movement are thus obtained:

The carriage 25 is moveable in the direction x along the basic stand 6.A displacement of the carriage 13 along the guide 14 allows a movementof the drill receiver 9 in the direction y.

The lathe attachment 12 has an axis of rotation B with the carriage 13,a further scale ring 36 being provided here too.

A further rotation through 180° is guaranteed by the release of thescrew bolt 11, this rotation taking place about the axis of rotation C.It thereby also becomes possible to insert longer workpieces to bemachined into the drill receiver 9.

Moreover, the rotation about the axis of rotation B can also bepermitted by means of a further quick-acting clamping lever 37. This isindicated only in FIGS. 1 and 3.

For the drill receiver 9, there is, in turn, a possibility of rotationthrough 360° which becomes possible as result of the release of afurther quick-acting clamping lever 38. As result of this release, arocker 39 with a corresponding scaling is relieved, so that the drillreceiver 9 can be pivoted about a further axis of rotation D.Furthermore, as shown in FIG. 2, between the rocker 39 and the bearingpedestal 10 are arranged four ball catches 40 which are respectivelyoffset at 90° and which allow four corresponding positionings.

The drill receiver 9 rests by means of a basic receiver 41 in a guidebush 42 which engages with a dovetail 43 into a corresponding groove 44of the rocker 39. The drill receiver 9 can thereby be exchanged quickly.Moreover, the mounting of the basic receiver 41 in the guide bush 42 isfree of play, a corresponding V-slot 45 being formed in the basicreceiver 41 and being assigned a ball catch 46.

Exact positioning and reverse grinding are possible with this ball catch46 and a scale ring 47 as results of a 12-division.

A quick-change receiver 48 is inserted into the basic receiver 41. Thisquick-change receiver 48 surrounds a collet chuck 49. The quick-changereceiver 48 is mounted in the basic receiver 41 by means of a locatingbore accurately in terms of concentric running and plane support and canbe locked in specific positions.

By means of various quick-change receivers 48, different types of colletchucks 49 can be used, as required. The quick-change receiver 48 is alsoobtainable as a cutter holder and quick-change holder with differentMorse taper sizes (MK 1-4) and as a drill chuck. The tightening of thecollet chuck 49 after the insertion of a corresponding drill 50 isobtained by means of a tightening nut 51. The bits of the drill 50 canbe aligned in the cross hairs of a magnifying glass 52.

FIG. 2 illustrates, furthermore, that the basic receiver 48 is arrangedin an additional fork 41a and with this forms an axis of rotation E.This fork 41a then also engages with the dovetail 43 into the groove 44.A pivoting of the receiver 9 about the axis of rotation E therebybecomes possible.

In a lower (sic) embodiment, a grinding device R1 according to FIG. 4has a double grinding unit 101 consisting essentially of a motor block102, via which a grinding wheel 103 and 104 is driven on each of the twosides. The double grinding unit 101 includes, furthermore, a tenon block105, via which it rests on the basic stand 106 (see FIG. 5) in a longhole.

The motor block 102 is retained via a corresponding quick-actingclamping lever 139. The double grinding unit 101 is thus designeddisplaceably, and furthermore it can be rotated, pivoted or changed overin reverse into various positions. This affords a time saving during thechangeover of the grinding wheels.

A quick-change holder 109 for a 6-jaw chuck 108 is received by means ofa receiving bolt 112 in a receiving bore 107 of a rocker holder 110. Therocker holder 110 possesses a scale 111 for setting the point angles fora left-hand or right-hand tool. The rocker holder 110 furthermorepossesses a receiving bore and is attached to an upper carriage 113which is moveable along a guide 114. This guide 114 consists essentiallyof a middle threaded spindle 115 and of two lateral guide rails 116 and117 (see FIG. 6). Both the guide rails 116 and 117 and the threadedspindle 115 pass through the upper carriage 113, but the threadedspindle 115 meshes with a corresponding internal thread in the carriage113. The guide rails 116 and 117 run free of play and are protectedagainst dirt.

The coarse setting of the upper carriage 113 is obtained as result of amovement along the guide 114, a lever 120 being pivoted counter to theforce of a spring 121 out of its engaged position with the threadedspindle 115. As soon as the desired position is reached approximately,the lever 120 is pivoted back so that its appropriately profiled endface engages into the thread flights of the threaded spindle 115. Thefine setting of the carriage position can now take place, this beingcarried out via a corresponding rotary grip 122 with a scaling 123. Thethreaded spindle 115 is rotated by means of this rotary grip 122, whilethe upper carriage 113 is held by the guide rails 116 and 117. Theadjustment is made within the 0.01 mm range.

The y-axis guide 114 is arranged on a carriage 118 which is connected tothe basic stand 106 via guide rails 127, 128 and through which athreaded spindle 129 passes.

The carriage 118 is guided on the basic stand 106 in a similar way tothat described in respect of the upper carriage 113. Here too, the rapidadjustment is made by means of a lever 119, whilst the fine setting iscarried out by a rotary grip 124 with an appropriate scaling 125 (seeFIG. 6).

The following possibilities of movement are thus obtained:

The carriage 118 is moveable in the direction x along the basic stand106. A displacement of the upper carriage 113 along the guide 114 allowsa movement of the quick-change holder 109 in the direction y.

The rocker holder 110 has an axis of rotation B with the upper carriage113, a further scale ring 111 being provided here too.

For the quick-change holder 109, there is, in turn, a possibility ofrotation through 360° which becomes possible as result of a release of arocker clamp 130. By this release, a rocker 131 with an appropriatescaling is relieved, so that the rocker 131 can be pivoted about afurther axis of rotation D. Furthermore, as shown in FIG. 4, between therocker 131 and the rocker holder 110 there are arranged four ballcatches 132 which are respectively offset at 90° and which allow fourcorresponding basic positionings.

The jaw chuck 108 is arranged on an indexing drum 126 in thequick-change holder 109 which engages by means of the receiving bore 112into the corresponding receiving bore 107 of the rocker 131. Thequick-change holder 109 can thereby be exchanged rapidly. Moreover, theindexing drum 126 is mounted free of play in the quick-change holder109, appropriate positionings being formed in the indexing drum 126 andthese being assigned a ball catch or a positioning or clamping screw.

Exact positioning and reverse grinding are possible with this ball catchand positioning and clamping screw and with a scale ring 134 as resultof a 12-division.

By means of various quick-change holders 109, different chucking systemscan be used, as desired, for example lathe-chisel and lever-chiselquick-change holders, 6-jaw chuck quick-change holders, ISO or SK40receiver quick-change holders, MK1 to MK4 quick-change holders andclamping-sleeve quick-change holders.

The working device P1 is shown in more detail in FIG. 7. The rockerholder 110 is arranged on a guide bolt 140 which is connected firmly tothe upper carriage 113. At the same time the rocker holder 110 isrotatable about the axis B and can be fixed in a desired rotary positionby means of a clamping screw 141.

The rocker 131 passes through the rocker holder 110, the rocker 131forming the axis of rotation D₁ with the rocker holder 110. The rocker131 and, together with it, the quick-change holder 109 with the jawchuck 108 can be rotated about this axis of rotation D₁. At the sametime, the rocker 131 is mounted free of play by means of a stay bearing142 and can be locked by means of a rocker clamp 130. In the presentexemplary embodiment, the rocker clamp 130 consists of a clamping screwwhich passes through a disk 143 and which comes up against the rockerholder 110. This disk 143 can be rotated about axis of rotation D₁, forwhich purpose a corresponding handle 144 is provided. The ball catch 132can also be seen, with which the rocker 131 can be fixed in variousbasic positions, for example in 4×90°.

Furthermore, on the disk 143 there is also provided a stop ring 136which interacts with a stop 145 on the rocker holder 110 in order tolimit the rotation of the rocker 131 about the axis of rotation D₁.

The receiving bore 107 serving for the reception of the receiving bolt112 can also be seen in the rocker 131. This receiving bolt 112 formsthe axis of rotation C₁, about which the quick-change holder 109rotates. At the same time, this axis of rotation C₁ is assigned twoscale rings 146 and 147, the scale ring 146 serving for setting thequick-change holder 109 and the scale ring 147 serving for theclearance-angle setting for surface grinding. Moreover, the receivingbore 7 of the rocker 131 serves for the reception of variousquick-change holders 109 which are shown by way of example in FIGS. 8 to11.

An appropriate headless screw 148 serves for fixing the receiving bolt112 in the receiving bore 107.

Moreover, the quick-change holder likewise forms with the rocker 131 aball catch 149, by means of which it is possible to fix the quick-changeholder 109 in various engagement positions in relation to the rocker131.

The quick-change holder 109 comprises the jaw chuck 108, an axis ofrotation A being formed here for the jaw chuck 108. Furthermore, the jawchuck 108 rests on the indexing drum 126 which has a 12-division and ascale ring 134. This scale ring 134 serves for the exact positioning ofthe tool bits and for reverse grinding.

Moreover, the jaw chuck 108 is held in the quick-change holder 109 bymeans of a clamping and positioning screw 133, here too a ball catchbeing provided for the exact alignment of the tool bits.

FIGS. 8 to 11 show various receivers which are held by the respectivequick-change holder 109. According to FIG. 8, it is a clamping-sleevequick-change holder 108a, according to FIG. 9 a lathe and plane chisel108b and according to FIG. 10 a so-called Sk40 receiver 8c (sic).However, these exemplary embodiments could be supplemented as desired.

We claim:
 1. Apparatus for grinding workpieces, comprising:a grindingdevice arranged on a basic stand, said basic stand having a first guide;a first carriage, mounted on said first guide, said first carriagehaving a second guide; a second carriage mounted on said second guide; arocker holder mounted on said second carriage through a guide bolt andhaving a first axis of rotation, said first axis of rotation forming acentral axis of said guide bolt; a rocker passing through said rockerholder so as to form a second axis of rotation between said rocker andsaid rocker holder, said second axis of rotation extending approximatelyperpendicularly to said first axis of rotation; and a receiver for saidworkpiece arranged on said rocker so as to form a third axis of rotationbetween said receiver and said rocker, said third axis of rotationextending approximately parallel and radially offset in relation to saidsecond axis of rotation, and said receiver being supported in relationto said rocker by a ball catch so as to provide quick and accuratepositioning of the receiver.
 2. Apparatus according to claim 1, whereina main axis of said receiver extends in a plane parallel to said firstaxis of rotations.
 3. Apparatus according to claim 2, wherein saidreceiver has an arm approximately parallel to said second axis ofrotation and said third axis of rotation, said arm holding a jaw chuck,a longitudinal axis of said jaw chuck being arranged in a planeapproximately parallel to said first axis of rotation.
 4. Apparatusaccording to claim 3, wherein said jaw chuck has an indexing drum whichinteracts with a scaling.
 5. Apparatus according to claim 1, whereinsaid receiver is inserted exchangeably into said rocker.
 6. Apparatusaccording to claim 5, wherein said receiver is arranged by means of areceiving bolt in a receiving bore of said rocker.
 7. Apparatusaccording to claim 6, wherein said receiving bolt has two scales. 8.Apparatus according to claim 1, wherein said rocker can be fixed by arocker clamp.
 9. Apparatus according to claim 8, wherein said rockerclamp passes through a disk which is connected to said rocker. 10.Apparatus according to claim 9, wherein said disk has a ball catchdisposed in relation to said rocker holder.
 11. Apparatus according toclaim 9, wherein said disk has a stop ring which interacts with a stopon said rocker holder.
 12. Apparatus according to claim 1, wherein saidfirst guide and said second guide each comprise threaded spindles andlaterally arranged guide rails which pass through said first carriageand said second carriage, said threaded spindles having correspondingrotary grips with scalings which can be reset to zero.
 13. Apparatusaccording to claim 1, wherein said first carriage and said secondcarriage each comprises a lever with an engagement profile for athreaded spindle, said lever being moveable out of an engaged positioncounter to a cup-spring assembly.
 14. Apparatus according to claim 1,wherein a main axis of said receiver extends in a plane parallel to saidfirst axis of rotation.
 15. Apparatus according to claim 1, wherein saidreceiver has an arm approximately parallel to said second axis ofrotation and said third axis of rotation, said arm holding a jaw chuck,a longitudinal axis of said jaw chuck being arranged in a planeapproximately parallel to said first axis of rotation.
 16. Apparatusaccording to claim 1, wherein said receiver is inserted exchangeablyinto said rocker.
 17. Apparatus according to claim 16, wherein saidreceiver is arranged by means of a receiving bolt in a receiving bore ofsaid rocker, said receiving bolt having two scales.
 18. Apparatus forgrinding workpiece, comprising:a grinding device arranged on a basicstand, said basic stand having a first guide; a first carriage, mountedon said first guide, said first carriage having a second guide; a secondcarriage mounted on said second guide; a rocker holder mounted on saidsecond carriage and having a first axis of rotation; a rocker arrangedon said rocker holder so as to form a second axis of rotation betweensaid rocker and said rocker holder, said second axis of rotationextending approximately perpendicularly to said first axis of rotation;a receiver for said workpiece arranged on said rocker so as to form athird axis of rotation between said receiver and said rocker, said thirdaxis of rotation extending approximately parallel and radially offset inrelation to said second axis of rotation, said receiver having an armbeing approximately parallel to said second axis of rotation, and saidreceiver being supported in relation to said rocker by a ball catch soas to provide quick and accurate positioning of the receiver and saidthird axis of rotation; a jaw chuck arranged on said arm of saidreceiver, a longitudinal axis of said jaw chuck being arranged in aplane approximately parallel to said first axis of rotation, said jawchuck having an indexing drum which interacts with a scale. 19.Apparatus for grinding workpieces, comprising:a grinding device arrangedon a basic stand, said basic stand having a first guide; a firstcarriage, mounted on said first guide, said first carriage having asecond guide; a second carriage mounted on said second guide; a rockerholder mounted on said second carriage and having a vertical first axisof rotation; a rocker arranged on said rocker holder so as to form asecond axis of rotation between said rocker and said rocker holder, saidsecond axis of rotation extending approximately perpendicularly to saidfirst axis of rotation; and a receiver for said workpiece arranged onsaid rocker so as to form a third axis of rotation between said receiverand said rocker, said third axis of rotation extending approximatelyparallel to said second axis of rotation, a ball catch being disposedbetween said receiver and said rocker so as to provide quick andaccurate positioning of the receiver.
 20. Apparatus for grindingworkpiece, comprising:a grinding device arranged on a basic stand, saidbasic stand having a first guide; a first carriage, mounted on saidfirst guide, said first carriage having a second guide; a secondcarriage mounted on said second guide; a rocker holder mounted on saidsecond carriage and having a vertical first axis f rotation; a rockermounted on said rocker holder so as to form a second axis of rotationbetween said rocker and said rocker holder, said second axis of rotationextending approximately perpendicularly to said first axis of rotation,said rocker being connected to a disk by a clamp, a ball catch beingdisposed between said disk and said rocker holder, a stop ring beingmounted on said disk for interacting with a stop mounted on said rockerholder; and a receiver for said workpiece arranged on said rocker so asto form a third axis of rotation between said receiver and said rocker,said third axis of rotation extending approximately parallel to saidsecond axis of rotation.